1. Field of the Invention - The present invention relates to a microminiature pump suitable for implantation in a living body and particularly to an implantable pump which is compatible with microelectronic circuitry fabrication techniques and materials.
2. Description of the Prior Art - Great strides have been made in the miniaturization of electronic circuits and the attendant reduction of power required to operate such circuits has led to the development of implantable medical devices which operate for long periods of time, years in fact, without replacement of the battery.
Similar developments have taken place in the field of mechanical devices, where the application of semiconductor processing techniques has led to the development of transducers and actuators made from material such a crystalline silicon. Several devices of this type are described in a paper "Silicon Mechanical Devices" by James B. Angell, Stephen C. Terry and Phillip W. Barth, published in the Scientific American, Apr., 1983.
These two fields have been developing simultaneously and have led to smaller electronic circuits and smaller mechanical devices. Despite the significant developments in the respective fields, there has not been a comparable advance in the art which combines electronics and mechanics. Thus, the expected single chip combinations of microminiature mechanical devices with micro circuits have not been forthcoming, and, in their stead, various hybrid arrangements such as shown in the paper "Silicon Mechanical Devices" have been the rule. While hybrid devices represent an improvement, they do not represent the ultimate in small size or reliability since the discrete components must be larger than would be possible with a complete, integrated, device, and the additional electrical connections required are potential failure points.
The present invention relates to a fluid pump in which all circuits and all the mechanical aspects are implemented in semiconductor technology and no hybrid components are required. The pump can be of the diaphragm or peristaltic type in which the sole moving part is a very thin section of silicon actuated by either electrostatic or electromagnetic force. If desired, check valves at the input and the output have seats or a diaphragm which are fabricated from the same silicon wafer as used to fabricate the pump diaphragm. Where check valves of the ball variety are used, the balls are coated with conductive material to allow electrostatic or electromagnetic actuation.
By virtue of the small size, low power requirements and construction material, the pump is suitable for dispensing drugs and movement of body fluids such as found in the eye.